Final answer:
The correct term for the increasing concentration of toxic substances through each trophic level of an ecosystem is biomagnification, which can have catastrophic effects on wildlife.
Step-by-step explanation:
The term that describes the process whereby toxic substances increase along trophic levels of an ecosystem is biomagnification. This process involves the increasing concentration of persistent, toxic substances such as pesticides and heavy metals in organisms at each successive trophic level. Classic examples include the accumulation of dichlorodiphenyltrichloroethane (DDT) in bird populations, which caused fragility in their eggshells leading to significant population decline. Biomagnification is a result of these toxic substances being fat soluble and stored in the fat reserves of organisms.